Capacitance transformer



Jan. 24, 1928.

E. D. EBY

CAPACITANCE TRANSFORMER Filed May 27. 1927 /0 Fig.2.

Inventor:

li-Iu igene QEby.

His Attor n ey' Patented Jan. 24, 1928.

UNITED STATES 1,657,249 PATENT OFFICE.

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My invention relates to capacitance or electrostatic transformer. Some electrical instruments and apparatus such as electrostatic measuring instruments may be operated with very little current. It sometimes ha pens however that the voltage of any available; source of current is too high and must be transformed to a lower value for direct application to the Instruments or apparatus. The voltage of the available source of current may be as high as a hundred thousand or two hundred thousand or more while the voltage desired for operatmg the instrument or a paratus may be very low,

perhaps only fi y volts or so. Thus, the

ratio of voltage transformation desired may be as high as two thousand or more to one. Instrument or current transformers of the usual type and having the necessary degree n of accuracy for this purpose and under these conditions would be very expensive and the general object of the invention is to prov de an improved capacitance transformer which may have a very high voltage transforma- .tion ratio and which shall be accurate, sim- "ple in construction and inexpensive.

The invention will be better understood from the following description taken in connection with the accompanying drawing 1n which Fig. 1 shows a convenient and efiicient sulating'cylinder 10. This insulating cylinder 10 may be conveniently formed by winding a sheet of paper on a temporary cylindrical form, the paper being impregnated with a suitable insulating compound. 'hvo conductive metallic sheets may be wound in with the aper to form the conductive layers 12 an 13.

After the cylinder 10 with its two conductive la rs or cylinders 12 and 18 is'formed, a small opening 14 is formed through the outer portion of the insulating cylinder and through the outer conductive cylinder 18, thus exposing the insulation between the two conductive cylinders. A smaller opening 15 is then formed through this intermediate insulation to expose the inner conductive cylinder 12 to which a terminal '16 is connected by soldering, this terminal 16 being brou ht out through the opening in the outer condimtive cylinder 13. A second terminal 17 is connected to the outer conductive cylinder throu h an opening in the outer portion of the cy inder 10.

The cylinder 10 ma be supported concentrically about the big tension conductor 11 in any suitable way. One convenient arrangement is shown in Figs. 1 and 2 where the cylinder 10 is built into a high tension bushing 18 of the usual oil filled type. The bushing 18 comprises outer and inner insulating sections, 19 and 20 respectively, connected by an intermediate metal sleeve 21 which is mounted in the cover of a casing 22. The casing 22 is ada ted to contain a body ofinsulating oil in w ich the lower or inner end of the bushing 18 may be immersed.

The terminal 17 of the outer conductive cylinder 13 is connected to the metal sleeve 21 and through this to the casin 22 which may be grounded. The'termina 16 of the inner conductive cylinder 12 is carried in a small bushin 23 through the sleeve 21 whence a conductor 24 is carried through a sealed opening in the casing 22 to a convenient point outside the casing.

The twocapacities between the hi h tension conductor 11 and the inner con uctive cylinder 12 and between the two conductive cylinders 12 and 13 are in series so that the voltage between the high tension conductor 11 and the outer conductive cylinder 13 will divide inversely as the values of the two capacities. Thus, if the two conductive cylinders 12 and 13 are very close together so that the capacity between them is very lar e as compared with the capacity between t e high tension conductor 11 and the inner conductive cylinder 12, then the voltage between the terminal 16 and the casing 22 or ground will be very small as compared with the voltage of the high tension conductor 11.

The outer or grounded conductive cylinder 13 is lon er than the inner cylinder 12 and extends evond it at each end so that the inner c linder 12 is shielded from outside distur ances. The sleeve 21 may include an extension 25 at each end rojecting beyond the adjacent ends of t e two conductive cylinders 12 and 13 to shield still further these cylinders from outside disturbances. This assures a practically constant ratio between the voltages to ground of the high tension conductor 11 and the inner conductive cylinder 12.

By bringing out the terminal 16 of the inner conductive cylinder 12 through an opening in the outer cylinder 13 and between the ends of the latter, distortion of the electrostatic field at the ends of these cylinders is avoided and the possibility of arcing and breakdown of insulation is reduced.

The invention provides a very simple and accurate arrangement for producing a very high ratio of voltage transformation where the secondary load is small. It has been described and illustrated in what is now believed to be its preferred form, but it will be apparent that various changes may be made without departing from the scope of the invention as defined in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, 1s,-

1. A capacitance transformer including a hi h tension conductor, and two conductive cylinders spaced concentrically about said conductor, the outer cylinder being connected to ground and extending beyond said inner cylinder at each end.

,2. A capacitance transformer including a hi h tension conductor, and two conductive cy inders spaced, concentrically about said conductor,--the outer cylinder being connected to ground, and the inner cylinder being provided with a terminal extending through said outer cylinder between its ends.

3. A capacitance transformer includin a hl h tension conductor, and two conductive cylinders spaced concentrically about said conductor, the outer cylinder being connected to ound and extending beyond said inner cy 'nderat each end, and the inner cyl-' inder being provided with a terminal extendindgsthrough said outer cylinder between 1ts en r 4. A capacitance transformer including a high tension conductor, a bushing surrounding said conductor and comprising a i grounded conductive sleeve, and two conuctive cylinders within said sleeve and' spaced concentrically about said conductolgi t v round'a high tension conductor, said cylinder supporting two conductive c linders, the

outer of said conductive cylin ers extendin beyond, the inner one at each end.

An insulating cylinder adapted to surround a high tension conductor, said cylinder supporting two conductive cylinders, the inner 0 said conductive cylinders being provided with a terminal extending throu h theisouter conductive cylinder between 1ts en I 8. An insulating cylinder adapted to surround a high tension conductor, said cylin-' der supporting two conductive cylinders, the outer of said conductive cylinders extending beyond the inner one at each end, and the inner of said conductive cylinders bein provided with a terminal extending throu the outer conductive cylinder between 1ts ends.

In witness whereof, I have hereunto set my hand this 25th da of May, 1927.

' hlUGENE D. EBY. 

